Safety switch



March 18, 1941. B. E. sHAw ,SAFETY SWITCH Filed Sept. ll, 1939 v Mv.

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Patented Mar. 18, 19

UNITED STATES PATENT OFFICE SAFETY SWITCH Burton E. Shaw, Bristol., Ind., assignor to Penn Electric Switch Co., Goshen, Ind., a corporation o! Iowa Application September 11, 1939, Serial No. 294,409

8 Claims.

reliable inoperation and accurate'in response toa predetermined rise in temperature of a heater element used to'operat'e the latch blade of the safety switch.

5i urtliei" object to provid-e a safety switch ferisce@ to e. blade eee-ets with coactiiie serving es 'ff o, @am

ts 'the om ascii llfafdly as falliti] of excess press.- e beleg ap' extent the coetact 1 to positie- 3 the eend-it i re= safety is still use, emit a trip lever in suoli ietcll .lade aiir, e, eomperisetoi lolarle that @oats l 'teem and they izc'tla siv one or the other espoi'zse to a rise or fail temperature.,

Still eeotieer object to provisie sefety switch mounted in suoli me ner the heating eier-oen;J is :emulated or' me sessel inside tile easing emi the latch eled'e is in front or" the compensator bleele seing mounted also baci; oi the panel a trip blade eoeetiog with time latch blade and the compensator enel extending through en opening le the panel.

furti-rer object is to provie a spring associated with the trip blade in such manner as to retain one of its ends in pivotal connection with the compensator blade and its other end latcheii on the free end o the latch blade in such manner that the spring operates the trip blade to open circuit position, once the latcli blade has moved to unlatched position.

Still a further object is to provide an arrange- (Cl. 20D-122) ment in which the compensator blade compensates for a rise of temperature inside the casing and in which the latch blade and the compeneater blade are arranged to compensate for any rise temperature thereof caused by flow of current through the velades.

with joe foregoing and other contemplated as Heil es obvious objects in View, the invention comprises the combination elements and ar er s so'eomoined as to coect and each other the performance e acoomplishment of the l prises in species or preferred mile-.toned ezio espeetively;

fe viewT o a resetting Le'rl, and

i the heel; of the e slot thereof rlrie bracket B a latch portion SG. teli portion is adapted to support the lower end of a latch blade of bimetal or thelilie secured to the portion l as a rivet ZG.

The f2-clamp 'portion receives a heater element E consisting of a coiled resistance Wire 2i embedded in insulating material 22, such as a phenolic product. Leeds 23 and 24 areprovided for the ends of the heater element H and may be connected in a burner circuit or the like for the purpose of raising the temperature of the heef-- ing element H during the time that the current is iiowing through the wire 2|. The c-clamp portion I1 is provided with a pair of ears 25 with which a clamp screw 26 is associated'for rigidly clamping the heater element H in position and to make good contact therewith for the purpose of conducting heat therefrom to the latch blade I9.

A second Abracket B' is provided for supporting a compensator blade 2-1 of bimetaliic material. The blade 21 is secured to the bracket B by a rivet 28 and the bracket in turn is secured to the panel I2 by a rivet 29.

The upper end of the blade 21 is formedwlth a pair of ears 30 and a notch 3|, as shown in Figure 8, to receife one end of a trip blade T. The trip blade T is notched at32 to coact with the ears 30, as shown in Figure 3, whereby a loose connectionbut one which will cause longitudinal movement of the blade T whenever the upper end lof the bladev 21 swings toward or away from the panel I2-is provided.

The blade T is split at 34a to provide a contact' portion 33 and a cam portion 34. The cam portion 34 is made of insulating material and may be secured to the blade T by rivets 35. 'I'he terminal end of the contact portion 33, as indicated at 33a, is silver-plated, and correspondingly the upper en'd of the latch blade I9 is silver-plated-as indicated at I9a, for the purpose of good electrical contact with each other when in the closed circuit position'of Figures 4 and 5.

The cam 34 has an inclined end 36 so related to the terminal end of the contact portion 33 that its obtuse corner falls short of the terminal end and its acute corner extends beyond it. Accordingly, as the latch blade I9 moves outwardly to they position of Figure 4, the obtuse corner of the cam 34 will be passed by the latch blade, and shortly'afterthe position of Figure 4 the terminal end of the contact portion 33 of the trip blade T will be free of the latch blade, as shown in Fig.. ur'e 5. It will be noted that the inclined end 36 of the cam 34 is now in engagement with the edge of the latch blade I9 under the influence of a 'spring 31 extending from the trip blade T to an extension 38 of the bracket B'. The spring 31 serves both to keep the right hand end of the blade Tin position and to urge the left hand end against the upper end of the latch blade I9 in Figure 4, and causes the cam 34 to take up the positions of Figures and 6 after the unlatching operation. This results in the cam 34' moving the latch blade I9 to the position of Figure 6, 55 where it cannot thereafter contact with the contact portion 33 ofthe trip blade until the switch is reset.

'I'he circuit to be broken by the safety switch at the contacts I9a and 33a is connected with wires 39 and 40. The wire 39 is soldered to an ear 4I of the bracket B and thewire 40 is soldered to the bracket B'. Accordingly, the current ows from the wire 39 through the bracket B, the latch blade I9, the trip blade T, the compensator blade 21 and the bracket B' to the wire40. It is thus obvious that the contact portions I9a and 33a arein the circuit and are operable to break it when the positions of Figures 5 and- 6 are assumed.

For resetting the trip lever T, I provide a r'esetting lever L having an upper portion 42 ex tending through a slot 43 of the casing'` IB. At the lower end, the lever L has a reduced extension 44 slidable ina notch 45 of a bracket 49. The bracket 46 is secured to the panel I2 by arivet' only when the resetting lever L is released.

Thereafter the safety switch will again open in response to predetermined energization of the heater element H without any possibility of holding the safety switch closed while a dangerous condition obtains.

Making the contacts at I19a and l33a. eliminates any separate switches or cutouts in addition to the latching mechanism and thus the manufacturing cost of the safety switch is reduced. The panel -I2 serves as a shield between the interior heat of the casing I0 and the latch blade I9, while the bracket B serves as a heat conductor winch reliably and accurately conducts the heat to the latch blade I9 and secures a degree of accuracy not heretofore' obtainable in a radiation type heater. Compensation is had both for current iiow through the blades I9 and 21 and for ambient temperature which may act upon both blades. Both blades are mounted so that upon heating they swing to the left (in Figure 2), thereby merely carrying the trip blade T with them in an obvious manner, and the spring 31 -does not interfere with this action in any way whatsoever. The result is a freedom of action that eliminates any variation in operation, of the safety switch, regardless of ambient temperature conditions.

My` invention has been described in the foregoing speciflcation and illustrated in the drawing more orless precisely as to details. It is to be understood, however, that changes may be made in the arrangement and proportions of parts and equivalents may be substituted 'without departing from the spirit and scope of the invention as set forth in the appended claims.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is: 1. In a safetyswitch, a casing, a panel therein, a latch bracket secured to said panel and having a portion projecting therethrough, a latch blade of bimetaliic material secured to said portion and adapted to warp away from said panel when heated, a heaterelement supported in a clamp portion of said bracket whereby -heat from said heater element is conducted through said bracket to said latch blade, a second bracket secured to said panel, a compensator blade of bimetallic material secured to said second bracket, a trip blade engagingthefree ends of said latch and compensator blades, a spring holding said. trip blade in engagement with said ends, said trip blade having a cam portion of insulating material and a 'contact portion, said cam and contact portions engaging said end of. saidlatch blade, said cam portion having an inclined end with its obtuse corner shorter than said contact portion and itsl acute corner longer than said contact, portion to eiect movement of said latch blade under the in uence of said spring to circuit-breaking position with respect to said contact portion after saic -latch blade warps to unlatched position relative thereto as a result of heat from said heater element, and circuit connections through said latch blade, the contact portion of said trip blade and said compensator blade by means of wires connected with said latch bracket and said second bracket.

2. In a safety switch, a casing, a panel therein, a latch bracket secured to said panel, a latch blade of bimetallic material and a heater element supported on said bracket wherebyheat from said heater element is conducted'through said bracket to said latch blade, a second bracket sew cured to said panel, a compensator blade ci bimetallic material secured to said second bracket,

a trip blade engaging the free ends of said latch and compensator blades, a spring holding said trip blade in engagement with said ends, said it trip blade having a cam portion of insulating material and a contact portion, said cam contact portions engaging said end of said latch blade, said cam portion having an inclined end to effect movement of sad latch blade under the influence of said spring to circuit-breaking position with respect to said contact portion after said latch blade Warps to unl-etched position relative thereto as a result of heat irom'said heater element. 3. in a safety switch, a latch bracket having a 5 clamp portion and a supporting portion, a latchv blade of birrletaliic material secured to said supporting portion, a heater element supported in said clamp portion of said bracket whereby heat from said heater element is conducted throngl'i said bracket to said latch blade, a compensator blade ci bin'letallic material, a trip blade engaging against the iree ends oi said latch and compensator blades, a spring connected with trip blade intermediate its ,mints of engagement with said latch and compensator blades to hold the trip blade in such engagement, seid blade having means 'to eiiect movement of said latchv bladeto circuit-breaking position with to said contact portion after said latch blade trarps to unlatched position relative thereto as a resuit of heat from said heater element.

el. in a safety switch, a latch having a clamp portion, a latch blade secinc portion whereby heat trom said heater conducted thro latch icm-cli latch compensator blade sir f position to and spaced said latch, blade, a trip blade having ends engaging the tree ends'of saidiatch com pensator blades, a spring connected with said tri biade intermediate said ends to hold the trir blade in engagement with said ends, said trip blade having a cam and a contact, said cem and contact engaging said end cf said latch blade, said cam effecting movement of said latch blade under the inuence of said spring to circuit-breaking position with respect to said contact after said latch blade warps to unlatched position relative thereto as a result of heat conducted from said heater element.

5. In asafety switch, -a panel, a latch bracket secured to one side of said panel and having a dit bracket secured to said side of said panel, a com portion projecting therethrough, a latch bladel pensator blade of bimetallic material secured to said second bracket, a trip blade engaging the free ends of said latch and compensator blades and extending through said panel, a spring biasing said trip blade to engage said ends, said trip blade having a. cam portion of insulating material and a contact portion, said cam and contact portions engaging said end of said latch blade, said cam portion having an inclined portion eiective to move said latch blade under the iniiuence of said spring to circuit-breaking position with respect 'to said contact portion after said .latch blade warps to unlatched position relative thereto and circuit connections through said latch blade, the contact portion of said trip blade and said compensator.

6. A safety switch comprising a latch bracket, a latch blade secured thereto,a heater element supported in a clamp portion oi said bracket whereby heat irom said heater element is conducted through said bracket to said latch blade, a trip blade engaging the free end oi said latch blade, a spring holding said trip blade in engagement therewith, said trip blade having a cam portion oi insulating material and a contact portion, saida cam and Contact portions engaging said end of said latch blade, said cam portion having an' inclined end with its obtuse corner shorter than said. contact portion and its acute corner longer than said contact portion to eiect movement of said latch blade under the influence oi said spring to circuit-breaking position with respect to said contact portion after said latch blade v/arps to uniatciied position relative thereto as a result oi heat from said heater element. 1. in a safety switch, a latch bracket, a latch blade secured to said latch bracket, a heater e ement supported in e, clamp portion of said latch bracket, Va trip bladeA engaging one end or said latch blade, a spring biasing said trip blade tol-- ward such engagement, said blade having a cam portion' and a contact portion, said caln and contact poitions engaging said end of said latch blade, said com portion operab e to eiect movement of said latch blade under the of s circuit-in'eakin;9 ccs.- id contact perlen alter ade watios to unlatciied position relative thereto and circuit connections through said latch blade and the contact portion of said trip blade.

8. in a Safety switch, a latch blade and a compensator blade both xedlv mounted at one end and extending substantially parallel to each other, the mounting means for said latch blade comprising a metallic bracket having a split tubular portion, a heater element clamped in said portion whereby the heat thereof is directly conducted to said latch blade, a; trip blade spanning the unmounted ends of said latch and compensator blades, and a spring connecte with said trip blade intermediate said latch and compensatdr blades and retaining said trip blade in contact with said unmounted ends of said latch and compensator blades, said latch bladejupon warping in response to the flow of heat from said heater element, releasing said trip blade. 

